Not sure how sciatica feels like, so this might or might not work but if you need short term relief try a back inversion machine
I've started to see this in some gyms and it helps me. Again mine was a slipped disc problem so the pain and feeling for sciatica could be completely different. As everyone in here says, best would be to consult a doctor first so they can let you know if you even need an x-ray or MRI.
The Gentle Return Inversion Machine - Hammacher Schlemmer